Effects of climate change on marine ecosystems in the southeastern Pacific: Multiple ocean stressors assessed through climate velocities

Anthropogenic climate change has triggered a cascade of impacts on marine ecosystems, often referred to as the “deadly trio”: warming, acidification, and deoxygenation. While these stressors will globally lead to the compression of marine habitats, their regional effects vary significantly and remain understudied. This is particularly true for the southeastern Pacific (SEP), which supports rich pelagic and benthic ecosystems closely linked to a complex seafloor featuring archipelagos and extensive seamount chains. Using model simulations from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), this study examines future regional-scale environmental changes in the SEP. Our analysis builds on the observation that the South Pacific Ocean Gyre is among the regions experiencing the least warming globally and that the epipelagic zone within the oxygen minimum zone may oxygenate in the future. These conditions may promote habitat expansion, which we assess using the climate velocities for temperature, oxygen, and pH. We demonstrate that, in a pessimistic near future (2015-2050), most regions show a potential climatic loss in the entire epipelagic layer. However, two broad areas benefit from conservation below the surface: a region in the tropics extending from 10°S-100°W to the east of Rapa Nui and the coastal region of Peru and Chile, extending up to the Desventuradas and Juan Fernández archipelagos. While the former is due to the slow warming rates, the latter results from both slow deoxygenation and oxygenation climate velocities along the coast of those countries, a zone that overlaps with the lowest changes in pH in the SEP, giving them a unique conservation value. We demonstrate that epipelagic ecosystems within the oxygen minimum zone may be less impacted by climate change than those outside of it.